Which big city is growing the fastest in Texas? Surprisingly, it's not Dallas.

Which surprising Texas city is growing even faster than Dallas?

Just how much bigger will Texas' big cities be in 25 years? A new study from LawnStarter.com reveals the expected population growth for Texas' five biggest cities by 2040, and a surprising North Texas spot ranks No. 1.

Fort Worth is poised for the most explosive growth among big cities in Texas, according to LawnStarter.

"The Texas Water Development Board's projections indicate Cowtown's headcount will approach 1.5 million in 2040. Translation: a population surge of nearly 84 percent from 2014 to 2040." Fort Worth boasts a strong job market, proximity to DFW Airport, and a vibrant downtown.

"Fort Worth has a long way to go to catch up to Dallas, but Fort Worth has an advantage that Dallas doesn't have: Fort Worth can annex. And Fort Worth has been smart enough to annex ahead of development," Bud Weinstein, a professor at Southern Methodist University who studies population trends, told KXAS TV.

Dallas ranks fourth on the list. Our expected population increase between 2014 to 2040 is slightly less than 20 percent. To put it in perspective, Dallas' projected population of 1,531,680 in 2040 will be the same as Phoenix's population in 2014.

Austin ranks second on the list, with an expected increase of slightly more than 45 percent.

San Antonio comes in third, with an estimated population increase of 33 percent. In 2040, San Antonio's population is expected to be just shy of 2 million residents. Houston, with an estimated population growth of 16 percent, ranks fifth.